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Michael Graziano

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Michael Steven Anthony Graziano [Scientist] (born 1967) is an American scientist and novelist who is currently a professor of Psychology and Neuroscience at Princeton University.[1] His scientific research focuses on how the cerebral cortex monitors the space around the body [2][3] [4] [5] [6] [7] [8] and controls movement within that space.[9] [10] [11] [12] [13] [14] [15] [16] Most notably he has suggested that the classical map of the body in motor cortex, the homunculus, is not correct and is better described as a map of complex actions that make up the behavioral repertoire.[17] His publications on this topic have had a widespread impact among neuroscientists but have also generated controversy.[18] [19] [20] [21] [22] [23] [24] [25] His novels [26] [27] rely partly on his background in psychology and are known for surrealism or magic realism.[28] [29] [30] Graziano also composes music including symphonies[31] and string quartets.[32]

Biography

Graziano was born in Bridgeport Connecticut in 1967 and spent his childhood in Buffalo, New York. He received his Bachelor of Arts degree from Princeton University in 1989 in Psychology. He attended graduate school in neuroscience at MIT from 1989 to 1991 and then returned to Princeton University to complete his doctoral degree in 1996, in Neuroscience and Psychology. He remained at Princeton University as a postdoctoral researcher and then as a professor of neuroscience and psychology.

Contributions in neuroscience

Graziano has made contributions in three areas of neuroscience: how neurons in the primate brain encode peripersonal space, how the motor cortex controls complex movement, and the possible neuronal basis of consciousness. These contributions are detailed in the following sections.

Peripersonal space

In the 1990s Graziano with Charles Gross described the properties of a set of multisensory neurons in the monkey brain. Building on the work of Hyvarinen and colleagues[33] [34] and Rizzolatti and colleagues[35][36] Graziano and Gross described a network of brain areas that appeared to encode the space immediately surrounding the body.[4][5][6][7][8]

Multimodal neurons in the monkey brain that encode the space near the body. Each neuron responds to touching a specific part of the body called the neuron’s tactile receptive field. The same neuron responds to visual stimuli in the space near the tactile receptive field. Two examples are depicted. From Graziano MSA and Gross CG (1998) Spatial maps for the control of movement. Current Opinion in Neurobiology, 8: 195 -201.

Each multisensory neuron responded to a touch within a specific "tactile receptive field" on the body surface. Each neuron also responded to a visual stimulus near or approaching the tactile receptive field. The "visual receptive field" was therefore a region of nearby space affixed to the relevant body part. Some neurons responded to sound sources near the tactile receptive field.[4] Some neurons also responded mnemonically, becoming active when a part of the body moved through space and approached the remembered location of an object in the dark.[5] The activity of these multisensory neurons therefore signaled the presence of an object near or touching a part of the body, regardless of whether the object was felt, seen, heard, or remembered.

Electrical stimulation of these multisensory neurons almost always evoked a complex, coordinated movement that resembled a flinching, blocking, or protecting action.[13] [14][15][16] Chemical inhibition of these neurons produced a "nerves of steel" state in which defensive reactions were inhibited.[13] Chemical enhancement of these neurons produced a "super flincher" state in which any mild stimulus, such as an object gently moved toward the face, evoked a full-blown flinching reaction.[13]

In Graziano’s interpretation,[37] these multisensory neurons form a specialized brain-wide network that encodes the space near the body, computes a margin of safety, and helps to coordinate movements in relation to nearby objects with an emphasis on withdrawal or blocking movements. A subtle level of activation might bias ongoing behavior to avoid collision, whereas a strong level of activation evidently causes an overt defensive action.

The neurons that encode peripersonal space may also provide a neuronal basis for the psychological phenomenon of personal space.[37] Personal space, described by Hall,[38] is the flexible bubble of space around each person that is protected from intrusion by other people.

The peripersonal neurons may also play a central role in the body schema[39] an internally computed model of the body first proposed to exist by Head and Holmes in 1911.[40]

An action map in the motor cortex

In the 2000s Graziano’s lab obtained evidence suggesting that the motor cortex might not contain a simple map of the body’s muscles as in classical descriptions such as Penfield’s description of a motor homunculus.[41] Instead, the motor cortex may contain a mapping of coordinated, behaviorally useful actions that make up a typical movement repertoire.

In their initial experiments, Graziano and colleagues used electrical microstimulation on the motor cortex of monkeys.[12][16] Most previous protocols in the motor cortex used very brief stimulation, such as for a hundredth of a second. Graziano applied the stimulation for half a second each time, on a behaviorally relevant time scale, in order to match the typical duration of a monkey’s reaching and grasping. The longer stimulation train in Graziano’s experiments evoked complex movements that included many joints and that resembled movements from the animal’s behavioral repertoire.

For example, stimulation of one site always caused the hand to close in a grip, the arm to bring the hand to the mouth, and the mouth to open. Stimulation of another site always caused the grip to open, the palm to face away from the body, and the arm to extend, as if the monkey were reaching to grasp an object. Other sites evoked other complex movements. The behavioral repertoire of the animal seemed to be rendered onto the cortical sheet.

This initial work became controversial because of the method of stimulation on a behavioral time scale. The method was not commonly used in the study of motor cortex[23] although it had been used in the study of other brain regions.[17] That controversy may have partially distracted from the other methods used to study the action map.[17] For example, computational models[9] show that when the complex movement repertoire of a monkey is arranged in a flattened map, with similar movements represented near each other, the map closely resembles the known arrangement of the monkey motor cortex.

In Graziano’s proposal, many of the complexities of the motor cortex, such as its overlapping maps of the body and its multiple areas with somewhat different mixtures of properties, may be a result of representing the many parts of the movement repertoire each with its own specialized computational requirements. Graziano[17] suggests that the action-map view does not contradict the more traditional view of motor cortex as a set of fields with differing functions. Instead, the action map may help to explain why motor cortex is divided into functionally distinct fields and why the fields are arranged spatially as they are.

Other researchers have since found a similar, ethological organization to motor cortical regions in monkeys, prosimians, cats, and rats.[20][42][43][19][18]

The brain basis of consciousness

Since 2010 Graziano’s lab has studied the brain basis of consciousness. Graziano[44][45] proposed that specialized machinery in the brain computes the feature of awareness and attributes it to other people in a social context. The same machinery, in that hypothesis, also attributes the feature of awareness to oneself. Damage to that machinery disrupts one’s own awareness.

The proposed "attention schema theory" was motivated by two sets of previous findings.

First, certain regions of the cortex are recruited during social perception as people construct models of other people’s minds.[46][47][48][49][50][51][52][53] These regions include, among other areas, the superior temporal sulcus (STS) and the temporoparietal junction (TPJ) bilaterally but with a strong emphasis on the right hemisphere.

Second, when these same regions of cortex are damaged, people suffer from a catastrophic disruption of their own awareness of events and objects around them. The clinical syndrome of hemispatial neglect, or loss of awareness of one side of space, is particularly profound after damage to the TPJ or STS in the right hemisphere.[54][55]

The conjunction of these two previous findings suggests that awareness is a computed feature constructed by an expert system in the brain. The feature of awareness can be attributed to other people in the context of social perception. It can also be attributed to oneself, in effect creating one’s own awareness.

Why construct the feature of awareness and attribute it to other people? In order to understand and predict the behavior of other people, it is useful to monitor other people’s attentional state. Attention is a data handling method by which some signals in the brain are enhanced at the expense of others. According to the attention schema theory,[45] when the brain computes that person X is aware of thing Y, it is in effect modeling the state in which person X is applying an attentional enhancement to signal Y. Awareness is an attention schema. In that theory, the same process can be applied to oneself. One’s own awareness is a schematized model of one’s own attention.

Books

Graziano writes literary novels under his own name and children’s novels under the pseudonym B. B. Wurge. His stated reason for the pseudonym is to ensure that children do not accidentally read the wrong category of book.[56] His novels have been praised for their originality, vividness, and surreal imagination.[28][29][30] His book for children, The Last Notebook of Leonardo, won the 2011 Moonbeam Award.

His books include:

Literary Novels:

The Love Song of Monkey (2008)
The Divine Farce (2009)
Death My Own Way (2012)


Children's Novels (written under the name B. B. Wurge):

Billy and the Birdfrogs (2008)
Squiggle (2009)
The Last Notebook of Leonardo (2010)


Books on Neuroscience:

The Intelligent Movement Machine (2008)
God, Soul, Mind, Brain (2010)
Consciousness and the Social Brain (2012, in press)


Books of music:

Three Modern Symphonies (2011)
Symphonies 4, 5, and 6 (2012)
Five String Quartets (2012)

References

  1. ^ Princeton University, Department of Psychology, Faculty Information
  2. ^ Aflalo TN and Graziano MSA (2008) Four dimensional spatial reasoning in humans. Journal of Experimental Psychology, Human Perception and Performance, 34: 1066-1077.
  3. ^ Graziano MSA, Cooke DF, and Taylor CSR (2000). "Coding the location of the arm by sight". Science. 290 (5497). Sciencemag.org: 1782–1786. doi:10.1126/science.290.5497.1782. PMID 11099420. Retrieved 2010-01-20.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c Graziano MSA, Reiss LAJ, and Gross CG (1999). "A neuronal representation of the location of nearby sounds". Nature. 397 (6718): 428–430. doi:10.1038/17115. PMID 9989407.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b c Graziano MSA, Hu XT, and Gross CG (1997). "Coding the locations of objects in the dark". Science. 277 (5323): 239–241. doi:10.1126/science.277.5323.239. PMID 9211852.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Graziano MSA, Hu XT, and Gross CG (1997). "Visuo-spatial properties of ventral premotor cortex". J Neurophysiol. 77 (5): 2268–2292. PMID 9163357.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ a b Graziano MSA, Yap GS, and Gross CG (1994). %7C "Coding of visual space by pre-motor neurons". Science. 266 (5187): 1054–1057. doi:10.1126/science.7973661. PMID 7973661. {{cite journal}}: Check |url= value (help)CS1 maint: multiple names: authors list (link)
  8. ^ a b Graziano MSA and Gross CG (1993). "A bimodal map of space: somatosensory receptive fields in the macaque putamen with corresponding visual receptive fields". Exp Brain Res. 97 (1): 96–109. PMID 8131835.
  9. ^ a b Graziano MSA and Aflalo TN (2007). "Mapping behavioral repertoire onto the cortex". Neuron. 56 (2): 239–251. doi:10.1016/j.neuron.2007.09.013. PMID 17964243.
  10. ^ Aflalo TN and Graziano MSA (2007). "Relationship between unconstrained arm movement and single neuron firing in the macaque motor cortex". J Neurosci. 27 (11): 2760–2780. doi:10.1523/JNEUROSCI.3147-06.2007. PMID 17360898.
  11. ^ Graziano MSA (2006). "The organization of behavioral repertoire in motor cortex". Ann Rev Neurosci. 29: 105–134. doi:10.1146/annurev.neuro.29.051605.112924. PMID 16776581.
  12. ^ a b Graziano MSA, Aflalo T, and Cooke DF (2005). "Arm movements evoked by electrical stimulation in the motor cortex of monkeys". J Neurophysiol. 94 (6): 4209–4223. doi:10.1152/jn.01303.2004. PMID 16120657.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ a b c d Cooke DF and Graziano MSA (2004). "Super-flinchers and nerves of steel: Defensive movements altered by chemical manipulation of a cortical motor area". Neuron. 43 (4): 585–593. doi:10.1016/j.neuron.2004.07.029. PMID 15312656.
  14. ^ a b Cooke DF and Graziano MSA (2004). "Sensorimotor integration in the precentral gyrus: Polysensory neurons and defensive movements". J Neurophys. 91 (4): 1648–1660. doi:10.1152/jn.00955.2003.
  15. ^ a b Cooke DF, Taylor CSR, Moore T, and Graziano MSA (2003). "Complex movements evoked by microstimulation of Area VIP". Proc Natl Acad Sci USA. 100 (10): 6163–6168. doi:10.1073/pnas.1031751100. PMC 156343. PMID 12719522.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ a b c Graziano MSA, Taylor CSR, and Moore T (2002). "Complex movements evoked by microstimulation of precentral cortex". Neuron. 34 (5): 841–851. doi:10.1016/S0896-6273(02)00698-0. PMID 12062029.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ a b c d Graziano, M. S. A., The Intelligent Movement Machine, Oxford University Press, 2008.
  18. ^ a b Ethier C, Brizzi L, Darling WG, Capaday C (2006). "Linear summation of cat motor cortex outputs". J Neurosci. 26 (20): 5574–5581. doi:10.1523/JNEUROSCI.5332-05.2006. PMID 16707808.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  19. ^ a b Ramanathan D, Conner JM, Tuszynski MH (2006). "A form of motor cortical plasticity that correlates with recovery of function after brain injury". Proc Natl Acad Sci USA. 103 (30): 11370–11375. doi:10.1073/pnas.0601065103. PMC 1544093. PMID 16837575.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  20. ^ a b Stepniewska I, Fang PC, Kaas JH (2005). "Microstimulation reveals specialized subregions for different complex movements in posterior parietal cortex of prosimian galagos". Proc Natl Acad Sci USA. 102 (13): 4878–4883. doi:10.1073/pnas.0501048102. PMC 555725. PMID 15772167.{{cite journal}}: CS1 maint: multiple names: authors list (link) Cite error: The named reference "Stepniewska&etal2005" was defined multiple times with different content (see the help page).
  21. ^ Helmuth L (2002). "Redrawing the brain's map of the body". Science. 296 (5573): 1587–1588. doi:10.1126/science.296.5573.1587a. PMID 12040152.
  22. ^ Krauzlis RJ (2002). "Reaching for answers". Neuron. 34 (5): 673–674. doi:10.1016/S0896-6273(02)00723-7. PMID 12062014.
  23. ^ a b Strick PL (2002). "Stimulating Research on Motor Cortex". Nat Neurosci. 8 (8): 714–715.
  24. ^ Moore, T (2004). "Homeland defense begins in precentral cortex". J Neurophysiol. 91 (4): 1456. doi:10.1152/jn.01085.2003.
  25. ^ Shadmehr, R (2009). "The motor cortex re-imagined". Nat Neurosci. 12 (6): 667. doi:10.1038/nn0609-667.
  26. ^ Graziano, M. S. A., The Love Song of Monkey. Leapfrog Press, 2008.
  27. ^ Graziano, M. S. A., The Divine Farce. Leapfrog Press, 2009.
  28. ^ a b [1] Geekscribe.com, book review from Oct. 18, 2009.
  29. ^ a b "book review from Sept. 14, 2009". Publishers Weekly. Publishersweekly.com. [dead link‍]
  30. ^ a b "book review from Dec. 3, 2009". Barnstable Patriot. Barnstablepatriot.com. 2009-12-03.
  31. ^ Graziano MSA (2011) Three modern symphonies and five character sketches in full score. Quercus Press, Teaticket, MA.
  32. ^ http://www.princeton.edu/~graziano/Music.html
  33. ^ Hyvarinen, J. (1981). "Regional distribution of functions in parietal association are 7 of the monkey". Brain Res. 206 (2): 287–303. doi:10.1016/0006-8993(81)90533-3. PMID 7214136.
  34. ^ Hyvarinen J and Poranen A (1974). "Function of the parietal associative area 7 as revealed from cellular discharges in alert monkeys". Brain. 97 (4): 673–692. doi:10.1093/brain/97.1.673. PMID 4434188.
  35. ^ Rizzolatti G, Scandolara C, Matelli M, and Gentilucci M. (1981). "Afferent properties of periarcuate neurons in macaque monkeys. II. Visual responses". Beh Brain Res. 2 (2): 147–163. doi:10.1016/0166-4328(81)90053-X.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  36. ^ Fogassi L, Gallese V., di Pellegrino G, Fadiga L, Gentilucci M, Luppino M, Pedotti A and Rizzolatti G (1992). "Space coding by premotor cortex". Exp Brain Res. 89 (3): 686–690. PMID 1644132.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  37. ^ a b Graziano MSA and Cooke DF (2006). "Parieto-frontal interactions, personal space, and defensive behavior". Neuropsychologia. 44 (6): 845–859. doi:10.1016/j.neuropsychologia.2005.09.009. PMID 16277998.
  38. ^ Hall ET (1966). The Hidden Dimension. Garden City, New York: Anchor Books.
  39. ^ Graziano MSA and Botvinick MM (2002). "How the brain represents the body: insights from neurophysiology and psychology". {{cite journal}}: Cite journal requires |journal= (help) In: Prinz W and Hommel B (ed.). Common Mechanisms in Perception and Action: Attention and Performance XIX. Oxford, UK: Oxford University Press. pp. 136–157.
  40. ^ Head H and Holmes G (1911). "Sensory disturbances from cerebral lesions". Brain. 34 (2–3): 102. doi:10.1093/brain/34.2-3.102.
  41. ^ Penfield W and Boldrey E (1937). "Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation". Brain. 60 (4): 389–443. doi:10.1093/brain/60.4.389.
  42. ^ Gharbawie OA, Stepniewska I, Qi H and Kaas JH (2011). "Multiple parietal-frontal pathways mediate grasping in macaque monkeys". J Neurosci. 31 (32): 11660–11677. doi:10.1523/JNEUROSCI.1777-11.2011. PMC 3166522. PMID 21832196.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  43. ^ Haiss F and Schwartz C (2005). "Spatial segregation of different modes of movement control in the whisker representation of rat primary motor cortex". J Neurosci. 25 (6): 1579–1587. doi:10.1523/JNEUROSCI.3760-04.2005. PMID 15703412.
  44. ^ Graziano MSA (2010). God, Soul, Mind, Brain: A Neuroscientist's Reflections on the Spirit World. Teaticket MA: Leapfrog Press.
  45. ^ a b Graziano MSA and Kastner S (2011). "Human consciousness and its relationship to social neuroscience: A novel hypothesis". Cog Neurosci. 2 (2): 98–113. doi:10.1080/17588928.2011.565121.
  46. ^ Brunet E, Sarfati Y, Hardy-Bayl&eacute MC, and Decety J (2000). "A PET investigation of the attribution of intentions with a nonverbal task". Neuroimage. 11 (2): 157–166. doi:10.1006/nimg.1999.0525. PMID 10679187.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  47. ^ Ciaramidaro A, Adenzato M, Enrici I, Erk S, Pia L, Bara BG, and Walter H (2007). "The intentional network: how the brain reads varieties of intentions". Neuropsychologia. 45 (13): 3105–3113. doi:10.1016/j.neuropsychologia.2007.05.011. PMID 17669444.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  48. ^ Fletcher PC, Happé F, Frith U, Baker SC, Dolan RJ, Frackowiak RS, Frith CD (1995). "Other minds in the brain: a functional imaging study of "theory of mind" in story comprehension". Cognition. 57 (2): 109–128. doi:10.1016/0010-0277(95)00692-R. PMID 8556839.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  49. ^ Gallagher HL, Happé F, Brunswick N, Fletcher PC, Frith U, and Frith CD (2000). "Reading the mind in cartoons and stories: an fMRI study of 'theory of mind' in verbal and nonverbal tasks". Neuropsychologia. 38 (1): 11–21. doi:10.1016/S0028-3932(99)00053-6. PMID 10617288.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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  53. ^ Vogeley K, Bussfeld P, Newen A, Herrmann S, Happé F, Falkai P, Maier W, Shah NJ, Fink GR, and Zilles K (2001). "Mind reading: neural mechanisms of theory of mind and self-perspective". Neuroimage. 14: 950–953.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  54. ^ Karnath HO, Ferber S, and Himmelbach M (2001). "Spatial awareness is a function of the temporal not the posterior parietal lobe". Nature. 411 (6840): 950–953. doi:10.1038/35082075. PMID 11418859.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  55. ^ Vallar G and Perani D (1986). "The anatomy of unilateral neglect after right-hemisphere stroke lesions. A clinical/CT-scan correlation study in man". Neuropsychologia. 24 (5): 609–622. doi:10.1016/0028-3932(86)90001-1. PMID 3785649.
  56. ^ "Book Review". Princeton Packet. 2008. {{cite journal}}: Unknown parameter |unused_data= ignored (help)

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